U.S. patent application number 10/456149 was filed with the patent office on 2003-11-13 for microspheres with sacrificial coatings for vaso-occlusive systems.
Invention is credited to Shadduck, John H., Truckai, Csaba.
Application Number | 20030212427 10/456149 |
Document ID | / |
Family ID | 29406980 |
Filed Date | 2003-11-13 |
United States Patent
Application |
20030212427 |
Kind Code |
A1 |
Truckai, Csaba ; et
al. |
November 13, 2003 |
Microspheres with sacrificial coatings for vaso-occlusive
systems
Abstract
A vaso-occlusive system comprising a catheter with a working end
that carries a fluid media for introduction into an aneurysm. The
fluid media carries a volume of microspheres, wherein each
microsphere has a sacrificial shell or coating that surrounds an
interior core portion of the microsphere. The core portions of the
microspheres comprise either a first or second polymerizing
composition, wherein interaction of such binary compositions will
cause polymerization of the media into a gel or solid media that
will occlude the aneurysm. An energy delivery means is provided
within the catheter working end to cause removal of the sacrificial
coatings of the volume of microspheres to thereby induce the
polymerization process.
Inventors: |
Truckai, Csaba; (Saratoga,
CA) ; Shadduck, John H.; (Tiburon, CA) |
Correspondence
Address: |
Csaba Truckai
19566 Arden Court
Saratoga
CA
95070
US
|
Family ID: |
29406980 |
Appl. No.: |
10/456149 |
Filed: |
June 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10456149 |
Jun 5, 2003 |
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09721812 |
Nov 24, 2000 |
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6458127 |
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60386544 |
Jun 5, 2002 |
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Current U.S.
Class: |
606/195 |
Current CPC
Class: |
A61B 17/12118 20130101;
A61B 17/12181 20130101; A61B 17/12136 20130101; A61B 17/12168
20130101; A61B 17/12022 20130101; A61B 17/12113 20130101; A61B
17/12045 20130101; A61B 2017/12068 20130101; A61B 17/12186
20130101 |
Class at
Publication: |
606/195 |
International
Class: |
A61M 029/00 |
Claims
What is claimed is:
1. A vaso-occlusive system, comprising: a catheter having a distal
working end with an interior chamber; a volume of microspheres
carried in said interior chamber, each microsphere having a
sacrificial shell portion that surrounds an interior core portion;
the core portions of the microspheres comprising either a first or
second polymerizing composition, wherein interaction of said first
and second compositions causes a polymerization process to thereby
create a substantially solid volume; and energy delivery means
within the catheter for causing removal of said sacrificial shells
of said volume of microspheres.
2. The vaso-occlusive system of claim 1 wherein said sacrificial
shell portion comprises a conductive polymer.
3. The vaso-occlusive system of claim 1 wherein said sacrificial
shell portion has a specified resistivity that causes its
disintegration upon a selected level of electrical current flow
therethrough.
4. The vaso-occlusive system of claim 1 wherein the microspheres
have a dimension across a principal axis thereof ranging between
about 10 nanometers and 100 microns.
5. The vaso-occlusive system of claim 1 wherein the microspheres
have a dimension across a principal axis thereof ranging between
about 100 nanometers and 50 microns.
6. The vaso-occlusive system of claim 1 wherein said sacrificial
shell portion has a specified resistivity that ranging between
about 0.1 ohm/cm. to about 50 ohms/cm.
7. The vaso-occlusive system of claim 1 wherein said sacrificial
shell portion has a specified resistivity that ranging between
about 0.1 ohm/cm. to about 10 ohms/cm.
8. The vaso-occlusive system of claim 1 wherein said sacrificial
shell portion comprises a polymer carrying a selected
chromophore.
9. The vaso-occlusive system of claim 1 wherein energy delivery
means within the catheter comprises at least one electrode coupled
to an electrical source.
10. The vaso-occlusive system of claim 1 wherein energy delivery
means within the catheter comprises an emitter coupled to a light
source.
11. A method of treating a vascular malformation at a targeted site
within a patient's vasculature, comprising the steps of: (a)
navigating a catheter working end to the targeted site in the
patient's vasculature; (b) introducing flowable media from the
catheter working end into the vascular malformation wherein said
flowable media carries a volume of microspheres, each microsphere
having a sacrificial shell portion that surrounds an interior core
portion of either a first or second polymerizing composition that
upon interaction cause a polymerization process; (c) activating
energy delivery means carried at the catheter working end to cause
disintegration of the sacrificial shell portions of the
microspheres; and (d) causing interaction of the first and second
polymerizing compositions thereby altering the flowable media to a
substantially solid media volume to provide occlusive media.
12. The method of claim 11 wherein the activating step delivers
electrical energy to the sacrificial shell portions of the
microspheres.
13. The method of claim 11 wherein the activating step delivers
electrical energy from a single polarity electrode carried in the
catheter working end.
14. The method of claim 11 wherein the activating step delivers
electrical energy between opposing polarity electrodes carried in
the catheter working end.
15. The method of claim 11 wherein the activating step causes the
thermal breakdown of said sacrificial shell portions of the
microspheres.
16. The method of claim 11 wherein the activating step delivers
light energy to the sacrificial shell portions of the
microspheres.
17. A vaso-occlusive system, comprising: a fluid media carrying a
volume of microspheres of first and second types, the first type of
microsphere having a sacrificial shell portion that surrounds an
interior core of a first composition; the second type of
microsphere having a sacrificial shell portion that surrounds an
interior core of a second composition; and wherein interaction of
said first and second compositions causes a polymerization of the
volume of fluid media.
18. The vaso-occlusive system of claim 17 further comprising
degrading means for degrading said sacrificial shell portions of
the microspheres.
19. The vaso-occlusive system of claim 17 wherein the degrading
means comprises an electrical energy source that cooperates with
radiosensitive compositions in said sacrificial shell portions of
the microspheres to thermally degrade said sacrificial shell
portions.
20. The vaso-occlusive system of claim 17 wherein the degrading
means comprises a light energy source that cooperates with
chromophores compositions in said sacrificial shell portions of the
microspheres to thermally degrade said sacrificial shell portions.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit of Provisional U.S. Patent
Application Ser. No. 60/386,544 filed Jun. 5, 2002 having the same
title, which application is incorporated herein by this reference.
This application is a Continuation-In-Part of U.S. patent
application Ser. No. 09/721,812 filed Nov. 24, 2000, now U.S. Pat.
No. 6,456,127, titled Polymer Embolic Elements with Metallic
Coatings for Occlusion of Vascular Malformations, which is
incorporated herein by the reference.
FIELD OF THE INVENTION
[0002] This invention relates to medical systems and techniques for
occluding aneurysms. More particularly, the vaso-occlusive provides
a fluid media for introduction into an aneurysm that consists of a
binary system of microspheres. Each microsphere has a sacrificial
coating that surrounds an interior core of the microsphere. The
cores of the microspheres comprise either a first or second
polymerizing composition, wherein interaction of such binary
compositions will cause polymerization of the media into a gel or
solid media that to occlude the aneurysm. An energy source is
carried at the catheter working end to cause removal of the
sacrificial coatings of the microspheres to induce the
polymerization process.
BACKGROUND OF THE INVENTION
[0003] Various devices and techniques have been developed for
occluding aneurysms or other vascular defects or deformations
(herein termed malformations). A common type of aneurysm treatment
utilizes a detachable coil that is fed into the aneurysm to
substantially occupy the aneurysm volume. The typical approach for
implanting an embolic coil in an aneurysm involves attaching the
coil to the distal end of a pushwire, and introducing the pushwire
and coil through a catheter lumen until the coil is pushed into the
aneurysm. The typical manner of detaching the coil from the
pushwire involves using a direct current to cause electrolysis of a
sacrificial joint between the pushwire and the coil. The coil can
then serve to mechanically occlude a significant volume of the
aneurysm and thereby reduce blood circulation within the aneurysm.
After a period of time ranging from several hours to several weeks,
the volume of the aneurysm can become fully occluded as blood clots
about the coil. Eventually, the aneurysm will be reduced and
reabsorbed by the body's natural wound healing process. This type
of vaso-occlusion system was disclosed by Gugliemli in U.S. Pat.
Nos. 5,122,136 and 5,354,295.
[0004] Another manner of treating an aneurysm was disclosed by
Gugliemli (see U.S. Pat. No. 5,976,131; 5,851,206) and is described
as electrothrombosis. In this particular approach, a catheter and
pushwire are used to push a wire coil into the aneurysm that is
connected to an electrical source. The system then delivers
radiofrequency (Rf) current to the coil which is adapted to heat
the blood volume within the aneurysm to cause thermal formation of
thrombus (see U.S. Pat. No. 5,851,206; Col. 5, line 5). The
conductive coil disclosed by Guglielmi in U.S. Pat. No. 5,976,131
has an insulated tip or other arrangements of insulation around the
coil to prevent localized "hot spots" (see U.S. Pat. No. 5,976,131;
Col. 3, line 53).
[0005] It is believed that several risk factors are involved in any
uncontrolled use of significant levels of Rf energy to cause
so-called electrothrombosis. Most important, the use of electrical
energy to cause current flow between a coil (first electrode)
within an aneurysm and a ground (a second body electrode) will
likely cause high energy densities and highly localized heating of
tissue that comes into contact with the coil. If the wall of the
aneurysm contacts the energized portion of a coil, there is a
significant danger of perforation or ablation of the aneurysm wall
that could be life-threatening. Further, the use of uncontrolled
energy delivery to an implanted coil could heat adjacent brain
tissue to excessive levels resulting in loss of brain function or
even death. For these reasons, the coils disclosed by Gugliemli
were provided with an insulating material covering the tip of the
coil that is most likely to come into contact the wall of the
aneurysm. However, it is still likely that unwanted localized
heating will occur within the aneurysm sac when attempting to cause
ohmic heating of the blood volume in an aneurysm by creating Rf
current flow between an electrode coil and a body electrode.
[0006] Another disadvantage of using the typical commercially
available wire coil is that the physician must estimate dimensions
and volume of the aneurysm and then feed multiple coils into the
aneurysm. The deployment of each coil is time consuming, and the
detachment of the coil from the introducer pushwire also is time
consuming.
SUMMARY OF THE INVENTION
[0007] In general, this invention comprises a vascular occlusion
system for treating aneurysms that provides a novel class of
continuous extruded polymer embolic elements that carry thin
metallic or conductive coatings that provide a specified
resistivity to electrical current flow. Alternatively, the polymer
element is fabricated with such specified resistivity by providing
conductive microfilaments or conductive particles embedded within
an extruded polymer element. The embolic element is introduced into
a targeted site in a patient's vasculature by a microcatheter
sleeve. The thin metallic coating allows the embolic element to be
soft and flexible, and more importantly, allows the physician to
select any desired length (and volume) of embolic element in vivo
for causing mechanical occlusion of the aneurysm. The system of the
invention also provides an electrical source and computer
controller for feedback modulation of power delivery with a first
(low) range and a second (high) range to accomplish two different
methods of the invention. The electrical source is coupled to an
electrode arrangement at the distal terminus of the catheter sleeve
that contacts the surface of the embolic element as it is slidably
deployed from the catheter. Thus, energy is delivered to the
resistive layer of the embolic element directly from the distal
terminus of the catheter sleeve. The catheter working end also
carries a thermocouple, coupled to feedback circuitry, for sensing
the temperature of the deployed embolic element and controlling its
temperature via power modulation. The embolic element can be
fabricated with a resistive metallic component to cooperate with
single electrode have a single polarity at the catheter working
end. Alternatively, the embolic element can be fabricated with
spaced apart metallic surface portions to cooperate with bi-polar
electrodes at the catheter working end.
[0008] In a method of using an exemplary system, the physician
pushes the embolic element from the distal terminus of a catheter
into a targeted site in a patient's vasculature thereby
mechanically occluding a selected volume of the aneurysm or other
vascular malformation. After disposing a selected length of the
embolic element within the targeted site, the physician then
actuates the electrical source via the controller to deliver
electrical current within a first (low) power range to the
conductive component of the polymer element from the electrode at
the catheter's distal terminus. The electrical energy delivery to
the metallic component that provides the specified resistivity
(e.g., preferably ranging between about 0.5 ohms and 25 ohms/cm. of
embolic element) causes resistive heating of the surface of the
deployed embolic element over a particular calculated length of the
element that extends distally from the electrode. This thermal
effect causes denaturation of blood components that results in the
formation of layer of coagulum about the deployed embolic element.
Additionally, the current flow within this first range causes
active or ohmic heating of blood proximate to the embolic element
in a manner that facilitates the formation of the coagulative layer
about the embolic element. During energy delivery, the temperature
sensor at the catheter working end sends signals to the controller
that are used to modulate power delivery to maintain the embolic
element at, or within, a particular temperature or range at the
catheter's distal terminus. By this manner of operation, the system
can controllably create a selected thickness of coagulum about the
surface of the embolic element. Thus, the initial deployment of the
selected length of the embolic element mechanically occludes or
occupies a selected (first) volume of a vascular malformation.
Thereafter, controlled energy delivery thermally induces a layer of
coagulative to form, thereby providing another selected volume of
material to occlude or occupy a selected (second) volume of the
vascular malformation. These methods of the invention provide means
to cause rapid mechanical occlusion of blood flow within the
malformation while preventing any significant energy densities in
the targeted site.
[0009] In the next manner of practicing a method of the invention,
the physician directs the controller and electrical source to
deliver current at a second (higher) power level to the metallic
component of the embolic element from the same electrode
arrangement at the catheter's distal end. This second power level
causes the metallic component together with the polymer core of the
embolic element to act like a fuse at the catheter sleeve's
terminus. This selected power level, within a fraction of a second,
can thermally melt or divide the deployed portion of the continuous
polymer embolic element from the remainder of the element still
within the catheter sleeve. This aspect of the method of the
invention allows the physician to select any length of embolic
element intra-operatively under fluoroscopy, which is not possible
in the prior art.
[0010] The invention advantageously provides a system and method
for intra-operatively disposing any selected length and selected
volume of an occlusive element in a targeted site in a patient's
vasculature to mechanically occlude a malformation.
[0011] The invention provides a system and method that does not
require the physician to pre-select a particular length of a coil
element for implantation in an aneurysm.
[0012] The invention provides a system and method that does not
require the physician to deploy multiple separate coil elements in
separate sub-procedures to occlude an aneurysm.
[0013] The invention advantageously provides a system and method
that utilizes a polymer embolic member that carries a metallic
component with a specified resistivity to current flow to thereby
allow controlled energy delivery within, and about, the member to
create a pre-determined thickness of coagulum about the embolic
member for mechanically occluding a vascular malformation.
[0014] The invention provides a system with feedback control that
modulates power delivery from a source to an embolic element to
maintain the embolic element at a specified temperature or within a
specified temperature range.
[0015] The invention provides a system with feedback control that
modulates power delivery to create a pre-selected thickness and
volume of occlusive material about an embolic element.
[0016] The invention provides a self-terminating electrical energy
delivery modality for creating a layer of occlusive material about
an embolic element.
[0017] The invention advantageously provides a system and method
that allows the delivery of electrical energy to an embolic element
within an aneurysm without the risk of localized high energy
densities.
[0018] The invention advantageously provides a system and method
that delivers electrical energy to an embolic element to increase
the volume of occlusive material in an aneurysm while eliminating
the risk of perforating the wall of the aneurysm.
[0019] The invention provides a system and method that delivers
electrical energy to an embolic element to increase the volume of
occlusive material in a cerebral aneurysm while preventing
collateral thermal damage to brain structure.
[0020] The invention provides an embolic member with a specified
resistivity by fabricating the a polymer member with at least one
very thin conductive surface layer.
[0021] The invention provides an embolic member with a specified
resistivity by fabricating the polymer extrusion with conductive
microfilaments embedded therein.
[0022] The invention provides an embolic member with a specified
resistivity by extruding a polymer matrix with conductive particles
embedded therein.
[0023] The invention advantageously provides a system and method
utilizes a polymeric element with first and second portions of a
metallic cladding that is adapted to serve as a bi-polar electrode
arrangement for creating a coagulative layer.
[0024] The invention provides a method for controllably creating a
coagulative volume about an embolic member by (i) controlling the
center-to-center distance between spaced apart conductive
components of the embolic member, and (ii) controlling the rate of
energy delivery between the spaced apart conductive portions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Other objects and advantages of the present invention will
be understood by reference to the following detailed description of
the invention when considered in combination with the accompanying
Figures, in which like reference numerals are used to identify like
components throughout this disclosure.
[0026] FIG. 1 shows a plan view of Type "A" vaso-occlusive system
with an elongate catheter sleeve that carries the polymer embolic
element made in accordance with the principles of the present
invention.
[0027] FIG. 2 is an enlarged cut-away view of the working end of
the catheter sleeve of FIG. 1 showing an exemplary polymer embolic
element with a metallic coating and an electrode arrangement
carried within the catheter sleeve.
[0028] FIG. 3 is a cut-away view of the working end of FIG. 2 with
an exemplary extension member adapted for pushing the polymer
embolic element member distally from the catheter sleeve.
[0029] FIG. 4 shows the manner in which the working end of FIG. 2
can be introduced over a guidewire.
[0030] FIG. 5A is view of view of a portion of an alternative
embolic element made up of multiple metallic coated filaments.
[0031] FIG. 5B is a view of the passageway in an alternative
embodiment of catheter sleeve that cooperates with embolic element
of FIG. 5A.
[0032] FIG. 5C is a perspective view of an alternative embodiment
of extension member adapted to grip the embolic element.
[0033] FIG. 6A is a view of the working end of the Type "A" system
of FIGS. I & 2 disposed in a blood vessel proximate to an
aneurysm.
[0034] FIG. 6B is a view of the working end of FIG. 6A after a
selected length of a distal portion of the polymeric member is
disposed in the aneurysm and formed into a tangled mass to occupy a
volume of the aneurysm.
[0035] FIG. 6C is a graphic view of portion of a polymer embolic
element with coagulum formed around the element by resistive
heating of the metallic surface to increase the volume of occlusive
material within a malformation.
[0036] FIG. 7 is a graphic view of a manner of practicing a method
of the invention in utilizing a selected level of electrical energy
to divide the implanted embolic element from a proximal portion of
the polymeric element still within the catheter sleeve.
[0037] FIG. 8 is a cut-away view of the working end of Type "B"
vaso-occlusive system showing a polymer embolic element with first
and second spaced apart metallic coatings made in accordance with
the principles of the invention.
[0038] FIG. 9 is a sectional view of an embolic element of a Type
"C" vaso-occlusive system wherein the embolic element comprises a
matrix of a polymer with conductive microfilaments embedded
therein.
[0039] FIG. 10 is a sectional view of an alternative embolic
element of a Type "C" vaso-occlusive system wherein the embolic
element comprises a matrix of a polymer with conductive particles
distributed therein.
[0040] FIG. 11 is a perspective view of a Type "D" vaso-occlusive
system that comprises a polymer sleeve having a mesh-like wall of
woven filaments having a specified resistivity.
[0041] FIG. 12 is an enlarged view of the woven filaments of FIG.
11 depicting conductive particles therein.
[0042] FIGS. 13A-13B are an enlarged views of the mesh-like wall of
woven filaments of FIG. 11 showing non-expanded and expanded
positions.
[0043] FIGS. 14A-14C are illustrations of the method of practicing
the invention, wherein:
[0044] FIG. 14A depicts the mesh-like polymer sleeve carries in a
non-expanded position at the working end of a catheter;
[0045] FIG. 14B depicts expansion of the mesh-like polymer sleeve
by expansion means comprising at least one balloon; and
[0046] FIG. 14C depicts the mesh-like polymer sleeve fused to the
vessel wall across the vascular malformation after delivery of
electrical energy to the filaments.
[0047] FIG. 15 is a schematic view of a Type "E" vaso-occlusive
system and first step in it method of use wherein a catheter
working end introduces a binary media of microspheres with
sacrificial shells into an aneurysm sac.
[0048] FIG. 16 is a schematic view of another step in utilizing the
Type "E" vaso-occlusive system to practice the method of the
invention.
[0049] FIG. 17 is a view of a final step in practicing a method of
the invention with the system of FIGS. 15-16.
DETAILED DESCRIPTION OF THE INVENTION
[0050] 1. Type "A" embodiment of vascular occlusive system. FIG. 1
shows an elevational view of a Type "A" catheter system 5 for
occluding an aneurysm or other vascular malformation. The catheter
system has a proximal handle or manifold 8 as is known in the art
that is coupled to an elongate microcatheter sleeve 10. FIG. 2 is a
cut-away view of the working end 11 of catheter sleeve 10 that
illustrates the metallic-coated elongate thread or filament element
12 corresponding to present invention that can be passed axially
through the cooperating microcatheter sleeve 10. The flexible
embolic element 12 defines a proximal portion 20a still carried
within catheter sleeve 10 and a distal thread portion 20b that is
pushed outward of the catheter. In this exemplary embodiment, the
embolic element 12 has an oval or flattened cross-section, but
other cross-sectional shapes are suitable.
[0051] In this exemplary embodiment, an internal bore or passageway
22 within the catheter sleeve 10 is adapted to carry the embolic
thread element 12 as well as to receive a slidable extension member
24 for pushing the polymer thread element 12 from the distal
termination 26 of the catheter (see FIG. 3). As can be seen in
FIGS. 2 & 3, the cross-sectional form of passageway 22 in the
catheter sleeve has a first oval-shape bore portion indicated at
28a for carrying the polymer thread element 12 and a second
round-shape bore portion indicated at 28b for slidably receiving
the round extension member 24. The second bore portion 28b also is
adapted for sliding over a guidewire 29 as shown in FIG. 4. It
should be appreciated that the embolic element 12 and cooperating
passageway 22 in the catheter sleeve 10 can be formed in several
cross-sectional shapes and configurations (e.g., round, flattened
and flexible, braided, etc.) and is shown in FIGS. 5A-5B with the
embolic element comprising a flattened braid of polymer
microfilaments. The cooperating extension member 24 may have and
suitable type of mechanism for pushing, pulling, helically
advancing, or otherwise expelling the embolic element 12 from
distal termination 26 of the catheter sleeve.
[0052] Referring now to FIGS. 1 & 2, it is possible to describe
several features and characteristics of embolic thread element 12
that adapt it for use in occluding an aneurysm sac or any other
vascular malformation. The embolic element 12 has a core 30 of a
continuous length of a flexible biocompatible polymeric material,
such as nylon, PET, polyamide, aramid fiber, urethane or
Kevlar.RTM.. The total length of the embolic element or member 12
may range from about 40 cm. to 2000 cm. The cross-sectional
dimension of embolic element 12 may range from about 0.0005" to
0.030" in a round cross-section element, or similar cross-sectional
area in any rectangular or other sectional shape. A suitable
polymer material can be fabricated in an extrusion process, for
example, by Polymicro Technologies LLC, 18019 N. 25th Ave.,
Phoenix, Ariz. 85023-1200. The polymer embolic element 12 further
carries a radio-opaque composition as in known in the art (e.g.,
BaSO.sub.4, BiO.sub.3) to allow fluoroscopic viewing of embolic
element 12 as it is maneuvered within a patient's vasculature. The
core 30 of the embolic element 12 preferably (but optionally) is
somewhat porous thus resulting in an irregular surface indicated at
33 to improve the gripping surface of thin-layer conductive or
metallic coating 40 on the embolic element as is described next.
FIGS. 5A-5B show an embolic element 12 comprising a plurality of
small diameter filaments 42 woven into a flexible braid, with each
filament having a metallic coating as described below. A braided
embolic element 12 such as depicted in FIG. 5A also would provide a
suitable surface 33 for gripping with extension member 24 as
described below. It should be appreciated that the flexible embolic
element may have a curved or coiled repose shape, and then be
straightened as it is passed through the catheter sleeve. Upon
deployment, the embolic element would again assume its repose
coiled shape to facilitate its introduction into an aneurysm.
[0053] As can be seen in FIG. 2, the embolic element 12 carries a
thin-layer conductive or metallic coating 40 that has a selected
electrical resistivity for accomplishing a method of the invention
described below. The metallic coating 40 may be any suitable
biocompatible material that can be formed in, or deposited on, the
elongate polymeric element 12, such as gold, platinum, silver,
palladium, tin, titanium, tantalum, copper or combinations or
alloys of such metals, or varied layers of such materials. A
preferred manner of depositing a metallic coating 40 on the polymer
element comprises an electroless plating process known in the art,
such as provided by Micro Plating, Inc., 8110 Hawthorne Dr., Erie,
Pa. 16509-4654. The preferred thickness of the metallic coating
ranges between about 0.00001" to 0.005". More preferably, the
coating thickness ranges between about 0.0001" to 0.001". Still
more preferably, the thickness of the conductive coating ranges
between about 0.0005" to 0.0007". As will be described below in the
Type "C" embodiment, the polymer element also may be extruded with
conductive filaments or particles embedded within the polymer
matrix of core 30 of the element.
[0054] Of particular interest, the combination of the core 30 and
metallic or conductive coating 40 of the embolic element 12
provides a selected resistivity to current flow that ranges from
about 1 ohm to 500 ohms per 10 cm. length of the embolic element 12
to cause controllable heating about the surface 33 of embolic
element 12. More preferably, the element provides a resistivity
ranging between about 5 ohms to 250 ohms per 10 cm. length. Still
more preferably, the core 30 and conductive coating 40 provide a
selected resistivity ranging between about 30 ohms to 60 ohms per
10 cm. length of the embolic element 12.
[0055] FIGS. 2 & 3 further illustrate that the distal end of
catheter sleeve 10 carries a conductive electrode surface indicated
at 44 about a distal region of bore portion 28a that carries
embolic element 12. The electrode 44 is coupled to electrical lead
46 that extends within the wall 48 of the catheter to its proximal
handle end and to electrical source 50 and controller 55. It should
be appreciated that the electrical lead 46 can be a part of a
helical braid reinforcement within the catheter sleeve. As can be
easily understood by viewings FIGS. 2 & 3, the elongate embolic
element 12 can be pushed distally from bore portion 28a, and no
matter the axial position of the embolic element, and electrode 44
will substantially contact the metallic surface 40 of the polymer
element 12. As will be described below in the method of the
invention, the electrical source 50 and electrode arrangement of
catheter 10 in combination with the metallic coating of the polymer
element 12 are adapted to (i) facilitate rapid occlusion of an
aneurysm, and (ii) to sever or divide the polymer thread element 12
to thereby implant any selected length of distal portion 20b of
polymer element 12 within in the aneurysm while retaining a
proximal length 20a of the polymer element in bore 28a of the
catheter. As shown in FIG. 3, the electrode 44 is shown for
convenience at the distal end of the catheter sleeve. Preferably,
the electrode 44 is spaced slightly inward or proximal from the
distal termination 26 of the sleeve to prevent any substantial
electrode surface from being exposed to the blood volume proximate
to a targeted treatment site.
[0056] In the system shown in FIGS. 2 & 3, the exemplary
polymer element 12 is very soft and flexible, for example, having
the flexibility characteristics of a common thread or suture. In
order to deploy the polymer thread element 12 from distal
termination 26 of catheter sleeve 10, this embodiment utilizes a
slidable extension member 24 that has unidirectional gripping
elements 57 (herein alternatively called barbs) about a distal
region 58 of the extension member 24. As can be understood in
viewing FIG. 2, an axial movement or projection of extension member
24 from sleeve 10 will cause the barb elements 57 to grip the
embolic element and pull it from bore portion 28a. When the
extension member 24 is moved proximally in bore portion 28b, the
barb elements will slide over surface 33 of embolic element 12 thus
leaving a selected length of the embolic element disposed outside
distal termination 26 of the catheter sleeve. The barb or gripping
elements 57 may be provided in extension member 24 may comprise
cuts into the surface of a polymer extension member 24.
Alternatively, the gripping elements may comprise a fiber or other
type of hair-like filament 59 bonded to the surface of an extension
member 24 as shown in FIG. 5C.
[0057] The catheter sleeve 10 while carrying the polymer embolic
element in bore portion 28a may be introduced into vasculature over
a guidewire 29 as shown in FIG. 4. The guidewire then can be
removed and be replaced by the extension member 24. To facilitate
the slidable introduction of the extension member 24 and grip
elements into bore portion 28b while embolic element 12 is carried
within bore portion 28a, the extension member may cooperate with a
very thin-wall sleeve 62 of Teflon.RTM. or any other suitable
material to prevent the gripping elements 57 from gripping the
embolic element 12 as the guidewire is replaced with the extension
member 24. As can easily understood from viewing FIG. 3, to expose
the distal portion 58 of the extension member 24 and gripping
elements 57, the thin-wall sleeve 62 can be retracted from the
gripping elements by pulling it proximally at the handle 8 of the
catheter.
[0058] The system 5 further provides feedback control mechanisms
within controller 55 for modulating energy delivery to electrode 44
and thereby to the conductive component of the embolic element.
Referring again to FIG. 3, at least one thermocouple 88 is provided
at either surface of electrode 44 to measure the temperature of the
electrode which is substantially the same as the surface
temperature of the embolic element in contact therewith. The
thermocouple 88 is linked to controller 55 by an electrical lead
(not shown). The controller 55 is provided with software and
algorithms that are adapted to modulate power delivery from
electrical source 50 to maintain the temperature of the embolic
element (or electrode 44) at a particular level or within a
particular temperature range, in response to feedback from the
sensor.
[0059] Now turning to FIGS. 6A-6B, the manner of using the catheter
system 5 to introduce the polymer embolic element 12 into a
cerebral aneurysm indicated at 100 or any other targeted vascular
site is shown. In FIG. 6A, it can be seen that working end 11 of
catheter sleeve 10 is introduced through blood 101 flowing in
vessel 102 until its distal termination 26 is positioned adjacent
to, or partially within, the aneurysm 100. Typically, the catheter
is guided to the aneurysm over guidewire 29 that is accommodated by
bore portion 28b of the catheter sleeve (see FIGS. 4 & 6A). In
FIG. 6B, it can be seen that guidewire 29 has been withdrawn from
catheter passageway 28b, and thereafter the extension member 24 has
been introduced back through the same passageway. The (optional)
thin-wall sleeve 62 as shown in FIG. 3 is withdrawn to expose
gripping elements 57 at distal portion 58 of the extension member.
FIG. 6B depicts an elongate distal portion 20b of the embolic
element 12 being disposed in the aneurysm sac 100 which has been
caused by pushing the extension member 24 to and fro thereby
causing the grip elements 57 to engage surface 33 of embolic
element 12 and successively carry small axial lengths of element 12
distally into the aneurysm under fluoroscopic control. In this
manner, any selected length of distal portion 20b of polymer
element 12, for example from about 5 cm. to 200 cm. for a typical
aneurysm, can be fed into the malformation. The selected length and
volume of embolic element 12 thereby displaces blood 101 and
occupies a selected (first) volume of the vascular
malformation.
[0060] As can be seen in FIG. 6B, the volume of aneurysm 100 can be
substantially occupied with the embolic element 12, depending on
its flexibility, to accomplish a first aspect of the method of the
invention. In effect, the embolic element 12 causes an initial
partial mechanical occlusion of the aneurysm volume by implanting a
selected volume of occlusive material (i.e., the entangled length
of polymer element 12) within the aneurysm which displaces a
similar volume of blood 101 and thereby slows blood flow through
the aneurysm and pressure therein. Next, a second novel aspect of
the method of the invention is practiced wherein electrical energy
is controllably delivered to embolic element 12 to increase the
volume of occlusive material within the aneurysm by adding a layer
of coagulum 104 about the polymer embolic element 12 thereby
occupying a second volume of the aneurysm.
[0061] More in particular, referring to FIGS. 6B & 6C, after
the selected length of distal portion 20b of polymer element 12 is
fed into aneurysm 100 under fluoroscopic control, the physician
actuates the electrical source 50 via controller 55 to deliver
electrical energy to electrode 44. The contact between electrode 44
and metallic surface 40 of polymer element 12 causes current flow
along the metallic surface 40 of the entangled element and within
the patient's body to a return electrode such as a ground pad in
contact with the patient's body. The selected resistivity designed
into the combination of metallic coating 40 and embolic element
core 30, as described above, causes resistive heating of the
element 12. The temperature of the surface 33 of the embolic
element (as well as slight active ohmic heating of blood about the
element 12) causes denatured blood products and coagulum to adhere
about surface 33 of the embolic element. As depicted graphically in
FIG. 6C, the thermally-induced coagulation of blood 101 causes a
substantial layer of coagulum 104 to form around the embolic
element 12 to thus provide a greater volume of occlusive material
within the aneurysm 100. In a preferred mode of operation, the
thermocouple 33 (see FIG. 3) together with feedback circuitry to
the controller 55 are used to modulate power delivery to electrode
44 to maintain the embolic element at the catheter terminus at a
pre-selected temperature level for a selected period of time. The
method of invention maintains the surface temperature of embolic
element 12 within a range of about 45.degree. C. to 100.degree. C.
More preferably, the surface temperature of the embolic element is
maintained within a range of about 65.degree. C. to 90.degree. C.
to create the desired coagulum. This aspect of the method of the
invention thus increases the volume of occlusive material within
the vascular malformation to further mechanically reduce blood
circulation within the defect. Thereafter, the occlusive material
(embolic element and coagulative layer) within the aneurysm then
rapidly will cause accumulation of platelets and other clotting
factors about the occlusive material to complete the occlusion of
the aneurysm volume as a result of the body's wound healing
response to the occlusive material volume within the aneurysm
100.
[0062] In accomplishing the above-described method of the
invention, the electrical energy delivery provided by source 50 and
controller 55 can be in the radiofrequency range and at a first
power level ranging between about 1 watt and 50 watts. More
preferably, the power level ranges between about 5 watts and 15
watts. It is proposed that current flow for about 5 seconds to 1200
seconds will cause the desired thickness of coagulative material to
form around the embolic element 12 to assist in the mechanical
occlusion of an aneurysm or other vascular defect. It should be
appreciated that the duration of power delivery is a factor in
creating a desired thickness of coagulative material on the embolic
element. However, the process of causing the formation of a
coagulative layer about the embolic element is essentially
self-terminating, which adds to the safety of practicing the method
of the invention. The method is self-terminating in the sense that
as the coagulative layer builds to the desired selected thickness,
the layer serves as an insulative layer and thereby prevents
further denaturation of blood compositions (or ohmic heating of
blood proximate to the embolic element.
[0063] The method of using an embolic element having a resistivity
in the selected range described above has the advantage of
preventing any possibility of creating energy densities ("hot
spots") within the aneurysm wall that could perforate the aneurysm
sac. The low power levels utilized in this method of the invention
can easily cause resistive heating of the metallic surface coating
40 for coagulation purposes, but cannot cause significant localized
current flows (i.e., energy densities) that could perforate a
vessel wall, or create energy densities that could cause ohmic
heating of collateral brain structure. Of particular importance,
the thermally-induced coagulative process is effectively
self-terminating since the temperature level at surface 33 of the
metallic coating 40 will become insulated by the coagulum, thus
preventing overheating of the interior or the aneurysm.
[0064] FIG. 7 graphically illustrates the next step of the method
of the invention that involves separation of the distal portion 20b
of embolic element 12 entangled within aneurysm 102 (see FIG. 6B)
from proximal portion 20a of embolic element 12 still within the
catheter sleeve 10. In order to accomplish the separation of the
embolic element 12 according to the invention, the physician
actuates electrical source 50 via controller 55 to deliver current
flow to electrode 44 that has a selected second (higher) power than
the previously described power levels. As can be understood in FIG.
7, the insulative coagulum around the embolic element 12 will
substantially prevent current flow at the second higher power level
to course through the endovascular media, thus eliminating the
possibility of high localized current densities. However, at the
interface 107 between electrode 44 and metallic surface in contact
with the electrode, the current flow will create a transient high
energy density in and about metallic coating 40 and core 30 of
element 12 to cause thermal melting of the polymer core to thereby
divide the embolic element 12. To divide the embolic element, it is
believed that a power level ranging between about 5 watts and 100
watts is suitable. More preferably, the power level is within the
range of about 10 watts to 30 watts. It is believed that current
flow for about 0.01 seconds to 20 seconds will divide the embolic
element. Following the division of the implanted embolic element
12, the catheter 10 that carries the proximal portion 20a of the
embolic element is withdrawn from the patient's vasculature.
[0065] The previously described means of dividing the embolic
element with electrical energy has the particular advantage of
allowing the physician to implant any desired length of the embolic
element 12 within an aneurysm or other vascular defect. The
physician simply can advance a length the polymer element into the
defect under fluoroscopy until the entangled volume appears
optimal, and then deliver electrical energy at the first and second
power levels to (i) add coagulative volume to the occlusive
material in the vascular defect, and then (ii) to separate the
implanted embolic element 12 from the remainder of the element
still within the catheter. This method of the invention, of course,
can be practiced for implanting an embolic element without
utilizing electrical energy to add a coagulative layer to the
embolic element as described above.
[0066] In another embodiment of embolic element 12, the polymer or
the metallic coating is formed in a coiled or curved shape and the
material has a memory of such a curved shape. The flexible embolic
element 12 then conforms to a generally linear configuration for
feeding through a catheter sleeve. Upon deployment beyond the
distal terminus of the catheter sleeve, the embolic element then
will substantially assume its curved or coiled shape which will
assist in its insertion into an aneurysm.
[0067] 2. Type "B" embodiment of vaso-occlusive system. FIG. 8
shows a cut-away view of a Type "B" catheter system 205 for
occluding an aneurysm, other vascular defect or malformation or any
targeted site within a patient's vasculature. The catheter system
is similar to the previously described embodiment and has a
proximal handle or manifold 8 coupled to an elongate microcatheter
sleeve 210 that terminates in working end 211. As can be seen in
FIG. 8, this system comprises a metallic-coated elongate member 212
that can be passed axially through the a cooperating bore 222 in
the microcatheter sleeve 210. This Type "B" system differs from the
previously disclosed system in that the flexible continuous embolic
member 212 (that defines proximal portion 220a and distal thread
portion 220b) functions in two alternative manners: (i) the
flattened embolic member 212 is substantially stiffened to allow it
to be pushed outward from a handle end 8 of the catheter sleeve
without requiring a pushing member or extension member as described
above, and (ii) the polymer embolic member 212 carries first and
second spaced apart metallic coating portions to act as resistive
elements and to further act as a bi-polar delivery system to
perform alternative methods of the invention in creating
coagulative material and in dividing the polymer embolic member 212
after implantation in a vascular malformation.
[0068] In this exemplary Type "B" system embodiment, the internal
bore 222 is shaped to receive the flattened embolic thread member
212 in a rectangular shaped bore portion indicated at 228a.
Additionally, the catheter sleeve is adapted to slide over a round
guidewire (not shown) that is accommodated by the round shape bore
portion 228b. In this embodiment, the embolic thread member 212
again has a body core 230 of a continuous length of a flexible
polymeric filament. The polymer embolic member 212 again carries a
radio-opaque composition.
[0069] As can be seen in FIG. 8, this alternative embodiment of
embolic member 212 carries first and second opposing thin-wall
metallic coating portions 240a and 240b that extend the length of
the embolic member 212. The metallic coating in this embodiment
again has a selected resistivity to current flow that ranges from
about 1 ohm to 500 ohms per 10 cm. length, although a lesser
resistivity also is functional for some methods of the invention.
For example, the opposing metallic coating portions 240a and 240b
can act as bi-polar electrodes as will be described below. In such
an application, the first and second metallic portions 240a and
240b extends along first and second sides 241a and 241b of the
entire length of the embolic member 212. It can be seen that these
first and second metallic surfaces define a center-to-center
dimension and can act as bi-polar electrodes, since the surface
portions are spaced apart on either side of a medial non-metallic
surface portion indicated at 243.
[0070] FIG. 8 further illustrates that working end 211 of catheter
sleeve 210 carries spaced apart first and second conductive
electrodes 244A and 244B on either side of bore portion 228a that
carries embolic member 212. The electrodes 244A and 244B are
coupled to electrical leads 246a and 246b in wall 248 that extend
to electrical source 50 and controller 55. As can be understood by
viewing FIG. 8, the elongate polymer member 212 is substantially
stiff so that it can be pushed distally from bore portion 228a from
the handle end of the catheter, and the electrodes 244A and 244B
will always be in contact with the respective metallic surface
portions 240a and 240b of the polymer element 212. Alternatively,
the embolic member can be pushed distally by an extension member as
described previously.
[0071] The manner of using catheter system 205 to perform the
methods of occluding a cerebral aneurysm 100 can be easily
described, still referring to FIG. 8. The elongate polymer member
212 is passed through the catheter sleeve 210 and thereby fed into
the aneurysm 100 similar to the graphic representation of FIG. 6B.
Thereafter, a guidewire (if used) is withdrawn from the catheter
passageway 228b. Thus, the aneurysm sac can be substantially
occupied with embolic member 212 to partially mechanically occlude
the aneurysm volume.
[0072] Next, the physician actuates electrical source 50 via
controller 55 to deliver electrical energy to common polarity
electrodes 244A and 244B. The contact between electrodes 244A and
244B and the metallic surface portions 240a and 240b of embolic
member 212 causes current flow along the metallic surfaces of the
entangled member in cooperation with a return electrode such as a
ground pad. The selected resistivity of the metallic surface
portions 240a and 240b of polymer element 212 then will coagulate
blood about the surface of the embolic member 212, generally as
described previously to add to the volume of implanted occlusive
material.
[0073] In a more preferred method of operation, the electrical
source 50 and system 205 is provided with circuitry that allows
controller 55 to programmably deliver bi-polar Rf current at a
first power level to electrodes 244A and 244B which are in contact
with the opposing metallic surface portions 240a and 240b of
polymer member 212 to cause current flow between the metallic
surface portions 240a and 240b. This manner of bi-polar current
flow is advantageous since it will not cause high current densities
in any endovascular media that might then threaten perforation of
the aneurysm wall. Such bi-polar flow thus will rapidly cause a
coagulative layer on the embolic member (generally between the
metallic surface portions 240a and 240b) to thereby add to the
volume of occlusive material within the aneurysm. In using the
paired metallic surface portions 240a and 240b in such a bi-polar
energy delivery modality, the metallic coatings may provide any
lesser resistivity to current flow for performing the method of the
invention.
[0074] In another energy delivery modality, the controller may
sequence delivery of mono-polar Rf current to the working end 211
in cooperation with a ground pad and bi-polar flow between the
paired metallic surface portions 240a and 240b to cause coagulum to
form about the embolic member 212. The system further may use a
thermocouple (not shown) and feedback circuitry as described above
to maintain the surface of the embolic member within the desired
temperature range as described above.
[0075] The use of the paired metallic surface portions 240a and
240b in a bi-polar mode is particularly adapted for use in the next
step of the method of the invention that involves separation of the
distal portion 220b of embolic member 212 entangled within aneurysm
102 (cf FIG. 6B) from proximal portion 220a still within catheter
sleeve 210. In using this embodiment, the physician actuates
electrical source 50 via controller 55 to deliver bi-polar Rf
current flow between electrodes 244A and 244B at a selected second
(higher) power level than used in the coagulation modality. In this
case, the second power level causes the core 230 of embolic member
212 to resemble a fuse as the current courses between the
electrodes to thus divide embolic member 212 at the distal
termination 226 of the catheter sleeve. It is believed that the
method of using bi-polar Rf current flow between paired electrodes
will allow separation of the embolic member 212 within a range of
about 0.1 to 10 seconds. Again, this embodiment of the invention
then allows any suitable length of embolic member 212 to be
introduced into the aneurysm--and then separated at the catheter
end.
[0076] In another Type "B" embodiment, the emboli member may have a
transverse section in the shape of a "C" (not shown) to partially
wrap around a guidewire or a pusher member (see FIG. 3). It can be
easily understood that such a cross-sectional shape would allow the
"C" shape to function in the fashion of rapid-exchange catheter
systems as are known in the art to insert over a guidewire.
Further, this embodiment would allow bi-polar electrode surfaces on
opposing and spaced apart inner and outer surfaces of the embolic
member to otherwise function as described above.
[0077] 3. Type "C" vaso-occlusive system. This alternative Type "C"
system uses a catheter sleeve as described in the Type "A"
embodiment above. This system differs only in the construction of
elongate embolic member 312 shown in FIGS. 9 and 10. The flexible
continuously extruded embolic member 312 again comprises a
substantially polymer core together with a conductive component
that provides the member with a specified resistivity. In one
alternative embodiment of Type "C" embolic member shown in FIG. 9,
the member 312 comprises a polymer matrix 345 that is co-extruded
with micro-filaments 350 of any suitable conductive material
embedded therein, such as tungsten, stainless steel or carbon
fiber. The micro-filaments 350 can be partially exposed at the
surface of the member to contact the electrode arrangement carried
at the distal termination of the catheter sleeve. In another
alternative Type "C" embolic member shown in FIG. 10, the member
312 comprises a polymer matrix 345 with embedded particles 360 of
any suitable conductive material to thereby provide the resistivity
specified above. The polymer conductive-resistive matrix of embolic
member 312 functions as a fuse to divide the embolic member at the
distal end of a catheter as described in the Type "A"
embodiment.
[0078] 4. Type "D" embodiment of vaso-occlusive system. Referring
to FIG. 11, the Type "D" vaso-occlusive system comprises a tubular
sleeve 400 that is assembled or woven from a polymer filament 410
of the type that was described previously (see FIG. 10). The
filament preferably is of the type illustrated (not-to-scale) in
FIGS. 11-12 wherein the filament 410 comprises a first polymer
portion 414 and a conductive portion 415. In one embodiment, the
conductive portion 415 can comprise conductive particles such as
carbon in a size ranging from about 1 nm to 10 microns. The
conductive portion 415 alternatively can be any other conductive
particle or filament of gold, silver or the like. The polymer
filament 410 is then woven into a sleeve as depicted in FIG. 11
that can be moved between a first contracted cross-section and a
second expanded cross-section. FIGS. 13A-13B depicts that woven
wall structure 418 of the sleeve 400 as it is expanded from the
first position (FIG. 13A) to the second position (FIG. 13B). The
polymer filament 410 can have any suitable diameter ranging from
about 0.0005" to 0.005". The polymer filament 410 also can of the
type described in the Type "A" embodiment above wherein the polymer
filament is made conductive by means of a very thin metallic
coating.
[0079] The diameter of the filament 410 can be any suitable
dimension to provide a sleeve 400 with a selected overall diameter
for adhering to the walls of a blood vessel. In use, the filament
410 is adapted to receive electrical energy from source 50 wherein
the conductive polymer conductive-resistive matrix is designed with
a specified resistivity within a particular temperature range that
will heat the filament to a selected temperature. The selected
temperature is adapted to fuse the filaments of the sleeve to the
vessel wall, as will be described next. The characteristics and
features of the conductive polymer matrix corresponding to the
invention are described in detail in co-pending Provisional U.S.
Patent Application Serial No. 60/366,992 filed Mar. 20, 2002
(Docket No. SRX-015) titled Electrosurgical Instrument and Method
of Use, which is incorporated herein by reference. In co-pending
Ser. No. 60/366,992, a conductive polymer matrix is disclosed for
controllably delivering energy to tissue for purpose of tissue
welding or tissue sealing, which is somewhat similar to the
objectives of the present invention. The method of the present
invention involves bonding a filament to tissue with the controlled
application of electrical energy, which can rely on the positive
temperature coefficient characteristics described in detail in
co-pending Ser. No. 60/366,992.
[0080] FIGS. 14A-14C next graphically depict the manner of using
the polymer matrix sleeve 400 to treat a vascular malformation. The
polymer filament sleeve 400 of FIG. 11 is particularly designed for
treatment of wide-neck aneurysms, some-times referred to as
"top-hat" aneurysms. Such malformations are often difficult to
treat with embolic coils or other embolic filler materials since
the vaso-occlusive materials may not be stable within the aneurysm
sac. The polymer filament sleeve 400 is thus adapted to extend
across the neck of aneurysm and thereafter be instantaneously fused
to the vessel wall with the application of electrical energy. The
filament sleeve 400 differs markedly from a conventional stent
since the polymer sleeve is flexible, has an extremely thin wall
dimension and becomes fused to the vessel wall for maintaining its
position. In contrast, a stent is not flexible which leads to
constant trauma to the vessel wall as it slightly changes in
dimension as the vessel wall expands and contracts during the
pulses of blood flow therethrough. Further, the stent remains in
position only because of its expanded strength that pushes against
the vessel wall.
[0081] FIG. 14A shows the polymer filament sleeve 400 is an
assembly being disposed over first and second expandable balloons
420a and 420b at the working end of an elongate flexible introducer
member 422. The sleeve 400 also can be carried over a single
balloon member or any other type of expansion structure. In FIG.
14A, the sleeve 400 is positioned across the large open neck 424 of
an exemplary aneurysm 425 in vessel wall 428. The introducer member
422 and at least one balloon can carry any suitable markings for
cooperating with an imaging system.
[0082] FIG. 14B next illustrates the expansion of the balloons 420a
and 420b that presses the woven wall structure 418 of the sleeve
400 against the walls 428 of the vessel. At least one inflation
lumen 432 extends through the introducer member 422 to a pressure
source as is known in the art.
[0083] Still referring to FIG. 14B, after the sleeve 400 is in an
expanded or deployed position against the vessel walls, the
electrical source 50 is actuated to deliver electrical current to
the conductive filaments 410 of sleeve 400. The very fine filaments
410 can be elevated to a selected temperature of between about
60.degree. C. and 90.degree. C. for an interval ranging from about
0.01 second to 5.0 seconds which will fuse the filaments to the
vessel wall 428. Preferably, the time interval of energy delivery
is less that about 1.0 second. The very rapid energy delivery to
the small cross-section filaments will prevent any substantial
damage to the vessel walls.
[0084] FIG. 14C illustrates the sleeve 400 deployed and fused to
the vessel walls after collapse of the balloons and withdrawal of
the introducer member. The use of the polymer sleeve 400 alone can
serve as a complete treatment for some types of aneurysms as the
wall 418 of the sleeve that extends across the neck 424 of the
aneurysm will cause a significant reduction in blood flow into and
around the aneurysm which will lead to thrombosis in the aneurysm
sac 425.
[0085] It should be appreciated that another sleeve 400 (not shown)
can have a less porous central wall portion that extends across the
neck 424 of the aneurysm to more effectively prevent blood flow
into the aneurysm sac 425.
[0086] In another manner of practicing the invention, an embolic
material may be introduced into the aneurysm sac 425 following
deployment of the polymer sleeve 400 across the neck 424 of the
aneurysm. Thus, the polymer sleeve 400 then can function as a mesh
to retain the embolic material within a wide-neck aneurysm. The
embolic material can be of any type known in the art, such as
embolic coils, foams or liquid agents that can be cured or
solidified within the aneurysm sac 425. FIG. 14B illustrates that
the introducer 422 itself can have a port 436 for introducing
embolic material into the aneurysm while the balloons are expanded
and stabilizing the sleeve 400 across the neck 424 of the
aneurysm.
[0087] The electrode connection between the introducer 422 and the
sleeve 400 can be on the surfaces of the balloons or within the
distal end of a bore that extends about the proximal end of the
polymer sleeve 400. The polymer sleeve 400 thus can be an
independent member in contact with an electrode or the sleeve can
detach from a connection to the introducer member by the fuse-type
means described previously. The system can operate with any type
and location of return electrode.
[0088] 5. Type "E" vaso-occlusive system. FIG. 15 provides a
schematic illustration of an exemplary Type "E" vaso-occlusive
system 500 that is adapted to fill an aneurysm sac with novel media
510 corresponding to the invention that can be altered from a first
flowable state to a second more solidified state. The system and
media 510 are directly related to the conductive-resistive polymer
matrix described in the Types "C" and "D" embodiments above and in
co-pending Provisional U.S. Patent Application Serial No.
60/366,992 filed Mar. 20, 2002 (Docket No. SRX-015) titled
Electrosurgical Instrument and Method of Use, referenced above.
[0089] In FIG. 15, the system of the invention is shown
schematically wherein a binary system of biocompatible agents are
encapsulated in microspheres 512a and 512b. The microspheres have
an exterior sacrificial shell portion indicated at 515 that is of a
conductive matrix material as described previously. The interior or
cores 522 of the microspheres 512 comprise either a first or second
composition (indicated at "A" or "B" in FIG. 15) that when mixed
together cause a polymerization process between the compositions
that will alter the media 510 from a flowable media to a
substantially non-flowable media, e.g., a solid or stiff gel-like
material. Thus, the media 510 in its flowable state-with first and
second types of microspheres therein-can be introduced into an
aneurysm from an opening in the distal termination of a catheter,
or from a port 530 in the side of the catheter's working end. Any
type of pusher mechanism can be used to expel the flowable media
510 from the catheter. Preferably, the flowable media 510 carries
radio-opaque materials or any other material that can cooperate
with an imaging system to allow the physician the ability to view
the introduction of the media into an aneurysm 525 (FIG. 15).
[0090] The sacrificial shell portions 515 of the microspheres can
be of a degradable material similar to materials described
previously that have conductive particles distributed therein. In
one embodiment, the shell material 515 carries particles that can
generally be described as "radiosensitive" in that they respond to
electromagnetic energy of a selected frequency. Thus, the catheter
corresponding to the invention can carry energy deliver means
(alternatively termed degrading means) for reducing, degrading,
disintegrating or otherwise fracturing sacrificial shell portions
515 of the microspheres. In one embodiment, the sacrificial shell
can be a wax or lipid with radiosensitive particles therein that
can be elevated in temperature (i) by resistive heating due to
current flow from an electrode 535 on the catheter working end or
(ii) by inductive heating from an emitter electrode as is known in
the art.
[0091] Thus, the invention provides a vaso-occlusive system that
comprises a flowable media 510 that carries a volume of
microspheres of first and second types, wherein each type of
microsphere has a sacrificial shell that surrounds an interior core
portion. The core portions, when allowed to interact, form a binary
system for polymerizing the media into a non-flowable gel or a
solid.
[0092] Now turning to FIG. 15, the distal working end 540 of a
catheter is shown schematically as being introduced to the region
opposing the neck 524 of an aneurysm 525. A pusher 542 is used to
expel a volume of media 510 from the port 530 which is directed
into the aneurysm. The axial movement and angular rotation of the
catheter is assisted by suitable markings on the catheter that
cooperate with an imaging system. During navigation of the
catheter, the port 530 can be maintained in a closed state by a
slidable cover, or a by burstable film or the like. The volume of
media 510 in FIG. 15 is illustrated for convenience with "A" and
"B" particles 512a and 512b that are grossly out of scale. In
practice, the microspheres can have a dimension across a principal
axis thereof ranging between about 10 nanometers and 100 microns.
More preferably, the microspheres have a dimension across a
principal axis ranging between about 100 nanometers and 50 microns.
FIG. 15 further shows that the catheter working end 540 carries an
optional balloon system 556 for engaging the walls 558 of the blood
vessel to insure that all of the media 510 is directed into the
aneurysm sac.
[0093] Referring next to FIG. 16, the distal working end 540 is
illustrating delivering energy to the volume of media 510 contained
in the aneurysm sac 525. The delivering of energy is indicated by
energy field ef that in this embodiment consists of electrical
current between first polarity (+) electrode 535 and a return (-)
electrode 565 that can be a ground pad as is known in the art. This
step of the method will resistively heat the sacrificial shell
portions 515 of the microspheres until they degrade or melt.
[0094] FIG. 17 next schematically illustrates the interaction of
the released "A" and "B" compositions 512a and 512b from the cores
of the microspheres that creates a uniform non-flowable volume of
media 510' that occludes the aneurysm sac. FIG. 17 further
illustrates the steps of collapsing the balloon member 556 and
withdrawing the catheter from the targeted site.
[0095] In another embodiment (not shown), the catheter working end
540 can carry opposing polarity spaced apart first and second
electrodes for delivering current to the conductive sacrificial
shell portions 515 of the media in what can be described as a
bi-polar electrode arrangement.
[0096] In another embodiment (not shown), the energy emitter can be
the terminal end of an optic fiber coupled to a light source, such
as a laser. The sacrificial shell portions 515 of the media can
carry a chromophore for cooperating with a selected wavelength of
the light source to again thermally degrade the sacrificial shell
portions 515 of the microspheres. In all other respects, the system
for occluding a vascular malformation would be the same.
[0097] Those skilled in the art will appreciate that the exemplary
embodiments and descriptions of the invention herein are merely
illustrative of the invention as a whole. Specific features of the
invention may be shown in some figures and not in others, and this
is for convenience only and any feature may be combined with
another in accordance with the invention. While the principles of
the invention have been made clear in the exemplary embodiments, it
will be obvious to those skilled in the art that modifications of
the structure, arrangement, proportions, elements, and materials
may be utilized in the practice of the invention, and otherwise,
which are particularly adapted to specific environments and
operative requirements without departing from the principles of the
invention. The appended claims are intended to cover and embrace
any and all such modifications, with the limits only being the true
purview, spirit and scope of the invention.
* * * * *